Fixing the iteration number again (I think)

In here, I fixed the iteration number:
gimli-org#643

In here, the iterator was changed from `range(maxIter) to `range(1, maxIter)`, without changing back PR643, making the thing wrong again.
gimli-org@d72b828

pygimli/frameworks/inversion.py

@@ -700,7 +700,7 @@ def run(self, dataVals, errorVals=None, **kwargs):
 
         for i in range(1, maxIter+1):
             if self._preStep and callable(self._preStep):
-                self._preStep(i + 1, self)
+                self._preStep(i, self)
 
             if self.verbose:
                 print("-" * 80)
@@ -730,7 +730,7 @@ def run(self, dataVals, errorVals=None, **kwargs):
                 self.showProgress(showProgress)
 
             if self._postStep and callable(self._postStep):
-                self._postStep(i + 1, self)
+                self._postStep(i, self)
 
             if self.robustData:
                 self.inv.robustWeighting()